Packaging machines are known that integrate into a single unit the various components necessary to form a container, fill the container with a liquid product, and seal the container. Such packaging machines typically feed carton blanks into the machine, seal the bottoms of the cartons, fill the cartons with a product dispensed from a product storage tank, seal the tops of the cartons, and off-load the filled cartons for shipping.
As the product is dispensed from the product tank during the packaging process, compensation must be made for the displacement of the product in the product tank. Thus, it is desirable to vent the product tank in order to compensate for the displacement of the product. Where the product is a liquid foodstuff, it may be necessary to maintain a sterile environment in the tank. Therefore, the tank cannot be vented to the open atmosphere.
One solution to the problem of venting the product tank while maintaining a sterile environment in the product tank is set forth in U.S. Pat. No. 5,009,339 to Hanerus et al. The '339 patent illustrates an apparatus for venting a plant for filling containers. The apparatus includes two control valves disposed at an outlet from the product tank and a vacuum pipe and pump assembly provided along an upper edge of the product tank.
Although a product tank can be vented in this manner at conventional operating speeds, new problems are presented as packaging machines are designed for ever-increasing through put capacities. Specifically, cartons are typically lifted into a sterile filling environment. At high operating speeds, sterile air that is displaced by lifting the cartons to be filled into the filling environment presents a problem that is not dealt with in the prior art, namely the problem of venting both the filling environment and the product tank. Additionally, vents disposed exterior to the tank present problems with CIP systems since the vent must necessarily be cleaned in a separate, manual cleaning step.